Lecture 10 - Evolutionary conservation of left/right asymetry Flashcards
Which organs show outward bilateral symmetry? [3]
- Eyes
- Ears
- Limbs
What happens during situs inversus asymmetry?
A reversal of the left/right axis
What happens during right isomerism asymmetry?
There is no spleen
What happens during left isomerism asymmetry?
There are two spleens
What are the two type of left/right axis determination in mouse?
- inversus viscerum: random placement of internal organs
- situs invertus: Complete reversal of all internal organs
What is the role of the Node?
Cilia at the node direct gene expression in a directional manner
How does the node cilia generate direction?
The cilia undergo rotation movement and generate leftward fluid flow
How is situs inversus caused by the cilia?
The cilia flow is reversed
How do the cilia set up asymmetry?
Calcium is directed to the left side of the node so the cilia at that side move more
True or False? Nodal signalling is symmetry at the node.
- False
- It is asymmetric
What happens after Nodal signalling is set up on the left side of the node?
- Pitx2 is expressed (Nodal-dependant)
- Lefty is activated (Nodal antagonist)
How is left/right asymmetry set up in sea urchin embryos?
- Rudiment forms on the left side of the larva
- Gives rise to adult organs
What does ate nodal expression in sea urchin embryos cause?
Activation of both TGF-beta inhibition and signalling
True or False? The rudiment can form without Nodal singalling.
True
What side of sea urchin embryos is Nodal expressed?
The right side
